Dry-cell electrode and method of making the same



Oct. 11, 1927. 1,644,746

K. H. W. RAMSAY DRY CELL ELECTRODE AND METHOD OF MAKING THE SAME FiledDec 26, 1925 I i v l NV ENTOR Karl Henrik Wilhqm RGMSQIH his ATTORNE a,ii, tar.

Patented KARL HENRIK WILLIAM RAMSAY, OF SUMMIT, NEW JERSEY, ASSIGNOR TDIAMOND ELECTRIC SPECIALTIES C031. OF NEWARK, NEW JERSEY, A CORPORATIONOF NEW JERSEY.

, nay-earn nnno'rnona Ann mnrnon or MAKING: THE same.

Application filed December 26, 1925. Serial No; 77,680.

. My present invention relates generally to dry cells and has particularreference to the type which embodies a bobbin comprising a carbon rodelectrode carrying a molded mix. Cells of this character generallycomprise a second electrode consisting of a zinc cup in which anelectrolyte is carried, and it has been found necessary to provide meansfor binding the bobbin together by an enclosing 1e envelope so as toprevent disintegration thereof when it is initially assembled with thezinc cup electrode by dippmgit into the electrolyte.

Means have been provided comprising bags of cheese-cloth or similarfabric which are generall tied about the bobbin by manual labor. I ageof this type have the essential property of being permeable to theelectrol e, but their utillzation entails much additional expense andtime due to the operation required to tie them in place.

Where I have attempted to enclose the bobbins in coatings of plaster ofParis or similar material instead of in fabric bags, I

have found that numerous disadvantages are entailed,- including thecomparatively long eriod required for the plaster to set, and t enecessity for preparing the plaster in comparatively small batchestominimize as far as possible, the waste which occurs even under favorableconditions due to the nature of the plaster in starting to set as soonas it is' moistened and in being incapable of resoftening after ithassetl Moreover, the comparatively lengthy association of the bobbinwith a moist material may have a detrimental effect upon the firmness ofthe bobbin; and the moisture in creases the possibility of the verydisinte- 40 gration which it is desired to guard against. It is anobject of the "present invention to provide a. coatin whose applicationCOIlStltutes an extrem y simple operation, entailing an almostnegligible. amount of time, and producing a dry protective film almostinstantaneous the film being not only permeable to e ectrolytic flow butsufficiently tough and strong to fulfill its binding purose.

Another object of the invention is to pro- :vide a bobbin-coating methodwherein waste of material is entirely prevented, the particular materialin contemplation being'of a character which permits preparation in largequantities without impairing its utility over a period of time, due tothe fact that its hardening 0r thickening may be controlled.

A further object is-to provide a method of coating during which thebobbin may be retalned in its driest possible condition, therebyincreasing the output efliciency by rate preventing wastage of bobbinsby disintegrat10n.-

My invention contemplates the use of a soluble material whose hardeningis due to the rapid evaporation of .the solvent rather than thecombination of the latter with the base, as in the case of plaster ofParis. The use of such a coating makes it pomible to prepare largequantitles thereof, and to util ze it as desired, without regard tolapse of time. Furthermore, a coating of this nature permits the timeand rapidity of drying to be controlled by the character of solventused. My invention also contemplates the addition to the coatingmaterial of various salts which are soluble in the electrolyte andWlllCh enhance the subsequent permeability of the dried coating. Y

Among the materials having not only the essential properties requiredfor a utilizat1on of this character, but also the desirablecharacteristics hereinbefore referred to, I

have found that varnishes, such as lacquers,

ms, and cellulose derivatlves, are very satlsfactory; and one embodimentof various my invention contemplates the utilization of materials ofthis character.

In a preferred embodiment, I coat' th bobbins with a varnish, andthereupon permit the usual solvent to evaporate. I refer to use solventswhich are capable o veriy.

7 rapid evaporation, such as the organic so vents illustrativelyexemplified by alcohol, whereby the dried film or membrane may beproduced in as short'a time as five seconds.

' Although the use of any particular var-'- nish or solvent is optional,depending upon the rapidity ,of drying and the nature of the coatingdesired, I have found it preferable to utilize a cellulose derivativesuch as pyroxylin dissolved in any of its well-known solvents, such asalcohol-ether, a'myl acetate, wood alcohol, etc. I have found thatcollodion lacquer, commonly known as collodion,

is particularly suitable and well adapted for the contemplated purpose;and in a preferred method of carrying out the invention, the collodionis pre-treated by the addition of zinc chloride or other suitable saltWhlCh is soluble in the electrolyte to be used, although suchpre-treatment is optional.

For the attainment of the foregomg objects and such other objects as mayheremafter appear or be pointed out, I have illustrated one form of drycell, constructed in accordance with my invention, in the accompanyingdrawing, which represents in elevational cross-section an assembled andcomplete dry cell.

I A carbon rod 10 isutilized as a base for the usual mix 11 which isapplied thereto by tamping or otherwise to constitute the bobbin. Themix 11 ma comprise the usual carbon granules mixe with manganese dioxideand preferably a small amount of zinc chloride or other suitable bindingagent. Before the bobbin is inserted into the electrolyte 12 which iscarried within the zinc cup 13, it is coated, preferably by dippin witha material dissolved in a solvent ca ab e of rapid evaporation; in apreferred em odiment, with a thin film or membrane of "varnish 14. Thebobbin is dip ed sufficiently, or similarly coated, to enc ose theentire bobbin, including the to and bottom thereof and a small portlonof t e projecting rod 10.

The electrolyte 12 may comprise a solution of zinc chloride and salammoniac mixed with flour and starch in a well-known manner to provide apasty mass which will subsequent y gelatinize. Suflicient electrolyte isplaced into the zinc cup to completely encircle the bobbin 11 after thelatter has been inserted into the cup into a position resting upon asuitable insulating washer 15 covering the base 13. Thereupon a secondwasher 16 is inserted to provide an air space 17 between itself and thelevel of the electrolyte 12. A cap 18 is then applied to the top of Ithe rod 10, and a suitable sealing substance 19, such as sealin wax, isapplied above the Washer 16 to se the battery, leaving only the endrtion of the ca 18 exposed.

Itwi be understood tii electrolytic flow is an essential characteristicof the coating 14. The permeability may be increased when desired by theaddition of suitable salts soluble in the electrolyte, or by permittingcoated bobbins to dry in an atmosphere of moist air. I prefer to preparethe coatm by mixing commercial collodion (U. S. P. in equal amounts witha saturated alcoholic solution of zinc chloride.

Although it is optional whether the bobbin is coated by spraying, directapplication,

.or dipping. or by any other method, I prefer to apply .the coating bydipping, for the reasons that absolutely no waste-1s entailed largequantities of the bobbins may be coated at permeability to 'ture ofcells, because no time need be wasted between the dipping operation andthe operation wherein the bobbins are inserted into the electrolyte.Moreover, absolutely no waste is entailed because the coating may beprepared invery large quantities since the eifects which standingmayhave upon the coating material may be easily remedied by the mereaddition of a'small amount of extra solvent. \Vhere va'rnish'is used,the nature of the varnish permits extremely thin coatings to be producedhaving thlcknesses in the nature of approximately .005 of an inch. Filmsof this thickness are however sufliciently tough and strong to formeflicient protective coatings, and this extreme thinness combined withthe absence of waste of material, permits many more bobbins, to becoated with a given amount of material than has been possibleheretofore. Furthermore, extreme thinness, combined with strength isextremely desirable in constructions of t 's character for the furtherreason that excessive resistance to electric current is effectuallyprevented.

. It will thus be seen that I have provided a I method of coatingwhich-is extremelyefiicient not only from the. standpoint of strengthand permeability of the membrane produced, but also from the standpointof economy, a great saving being effected not only by the elimination ofwaste but by the reduction of; labor required, time expended, andmaterial used.

It will be obvious that various changes may be made in' the detailsherein described for the purpose of explaining the nature of myinvention without departing fromthe sp1r1t and sco e of the invention asexpressed in the appen ed claims.

I claim 1. A- dry cell bobbin having a surface coating of an inherentlypermeable varnish forming an inte' 'ral art thereof.

2. A dry cel bob in having a surface coating of varnish mixed with asubstance soluble in the electrolyte of the cell.

3. A dry cell bobbin having an inherently permeable surface coatingconsisting essen-.

tially of pyroxylin.

4. A dry cell bobbin having a coating of varnish mixed with zincchlorlde.

5. The method of preparing a dry cell bobbin which comprises molding amaterial into electrode form susceptible of disinte ation, coating saidform with a ra idly ing varnish which on drying eposits a coherentsupporting surface film permeable v to electrolytic flow, and causingthe same to dry.

6. The method of preparing a dry cell bobbin which comprises formin anelectrode body which is susceptible of disintegration, coating said bodywith a rapidly drying collodion solution which on drying deposits acoherent supporting film permeab e to Electrolytic flow, and causing thesame to 27 The method of preparing a dry cell bobbin which comprisesmold' a material into electrode form susceptible o disinte ation,coating said form with a rapidly ying varnish containin a substancesolub e in the electrolyte of t e cell and which on drying deposits acoherent supporting film permeable to electrolytic flow, and causing thesame to dry. 7

8. The method of preparing a dry cell. bobbin which comprises formin anelectrode body which is susceptible of disintegration, coating saidbody'with a rapidly drying collodionsolution containing a substance 25soluble in the electrolyte of the cell which on drying deposits acoherent supporting film permeable to electrolytic flow, and causing thesame to dry.

In witness whereof, I have signed and 30 sealed this specification this24th day 0 November, 1925.

KARL HENRIK LAM RAMSAY.

